1. Field of the Invention
This invention relates to a control assembly for a flow dispenser, a control valve and integral monitor of pressure drop in the flow.
2. Summary of the Prior Art
It is known, particularly from French Pat. Nos. 2 180 484 and 2 180 485, to provide a control assembly comprising a flow dispenser with linear displacement including a piston capable of sliding within a casing having an upstream chamber operable at a pressure P.sub.1 and connected at the supply side with a pump and a downstream chamber operable at a pressure P.sub.2 and connected directly or indirectly to a user installation such as a gas turbine, the piston comprising a metering section enabling the two chambers to communicate through a passage having a section controlled by the sliding of the piston, a control valve with linear displacement formed by a slide capable of sliding within a casing having an upstream chamber and a downstream chamber and adapted to provide communication between the two chambers in response to sliding motion of the slide brought about by a change in the pressure drop P.sub.1 -P.sub.2 detected by a pressure drop detector, the downstream chamber of the control valve being connected to the selected one of the two chambers of the flow dispenser and the upstream chamber being connected to a selected point of the circuit as a function of the type of pump used, so as to maintain the pressure drop P.sub.1 -P.sub.2 constant.
In the two patents referred to which relate to a main control, a volumetric pump is used which delivers a constant volume, and the purpose of the control valve is, in response to the detection of an increase in the pressure drop, to divert the excess of fuel between the pump and the dispenser in order to maintain constant the pressure drop within the dispenser. It is known that this is a condition required for the flow of fuel supplied to the injectors of a post-combustion or other fuel system of a gas turbine, which is proportional to the section of the passage and to the square-root of the pressure drop, and varies linearly with the displacements of the dispenser piston (if the section of the passage is proportional to the displacement of the piston). It is also known within the sphere of post-combustion controls of assemblies of the type referred to use a centrifugal pump which delivers at a pressure substantially independent of the flow. In this prior proposal, the maintenance of pressure drop at a constant value within the dispenser is achieved whilst connecting the control valve in series with the dispenser, so as to produce a supplementary throttling which enables action on the upstream or downstream pressure of the dispenser and thereby to re-establish, in response to a change, the pressure drop at the value determined for this flow.
Furthermore, it has already been proposed, particularly in French Pat. No. 2 288 866, to construct a control assembly comprising a dispenser and a control valve integrated therewith.
An object of the present invention is to continue progress in the miniaturization of fuel control systems.